Cutting carbs the key for busy Allison Janney

“The Duff,” Allison Janney’s new movie, takes its name from an acronym for the Designated Ugly Fat Friend.

But in high school the actress was anything but. She was too tall to hold extra calories.

“I didn’t even have a date until college,” she says. “I was so tall in high school that I wasn’t really anybody’s catch at 5-foot-11 by senior year. I don’t even know when I stopped growing, but I was taller than all the guys. I was ridiculously tall.

“I was friends with the pretty girls in high school — and the guys would befriend me to get to the pretty girls. I was everyone’s best friend. I was the Duff in my own way, but I think everyone is the Duff for some reason.”

The Ohio native is now 55 and plays Mae Whitman’s mother in the coming-of-age film due out Friday. Janney also stars on the CBS hit “Mom” and in the current Hugh Grant film “The Rewrite,” about competitive English professors. She’s by the book and he’s a Hollywood screenwriter looking for a career time-out.

How does she stay healthy to do it all? “Besides the hair and makeup that make me look better?” Janney teases. “The truth is, I lost weight years ago by cutting out carbs. I feel great and have tons of energy, but I do my eating plan my way.”

In other words: She’s not rigid about it.

“I still like a cocktail now and then, and I love chocolate. But on most days, I try to stick to the protein and veggies and skip the other stuff,” she says.”What helps is I know that I can have that treat. I’m not denying myself.”

Does she beat herself up if she sneaks a doughnut at work? “Never,” Janney says. “I’m not always successful at sticking to my eating plan, but I try, which is the important thing. That means I’m more successful then not. It’s about adding up the good days.”

Janney now stands at around 6 feet tall. “My height helps, but the truth is, eating is still a challenge,” she says. “I work on a TV set where there is an unbelievable craft services table I walk by all day long. There are tons of cookies, cakes and brownies. For lunch, there is homemade mac and cheese.”

How does she cope? “I really just try to put blinders on and not look at it,” she insists. “It’s not easy, but every day we make our choices. This week, I haven’t made it past the brownies every single day. I don’t know why, but I decided I deserved a brownie … or two … or three. I figure that I’m working so hard that I must be burning the calories.

“If you slip up like me, you can’t be mad at yourself. Just start again,” she said.

Janney’s other healthy living tips:

• Be physical. “I do Pilates and walk the dog,” she says. “I love doing both, so I actually do it. My joke is I love Pilates because I get to lie down. The truth is it really has reshaped my body.”

• Work out to keep your body strong. “I have an upcoming episode of “Mom’ where I hurt my back. I had trainers helping me walk around like someone with a back injury. It reminded me that you want to keep your back and core strong because the alternative isn’t good.”

• Be proud of your body. “In that same scene on ‘Mom,’ I’m behind a shower curtain trying to keep it up around my naked body,” she says. “It was fun, but brought up a lot of issues.” Could it have been a nude scene? “I finally decided that as long as they light me right and I look good, well then who cares!”

• Encourage your kids to be physical. “My parents made me do physical things like ice skating, ballet and modern dance. I did those things until I was taught to stand up straight and own my height. I was the girl who previously knew how to plie under a long skirt so I looked shorter.”